Baltimore bridge collapse: Mass casualties feared as people fall into Patapsco River

• Singapore-flagged cargo ship was heading to Sri Lanka.
• Authorities are currently searching for 20 people.
• Francis Scott Key is one of world's longest truss bridges.
  

At least seven people dropped into the Patapsco River after a bridge dramatically collapsed into the water in Baltimore, prompting a rescue operation and preparations for a mass casualty incident.

Footage of the tragic incident showed the Francis Scott Key Bridge collapse after a Singapore-flagged cargo ship crashed into it as the vessel was heading to Colombo, Sri Lanka, the US media reported.

The ship caught fire and smoke billowed from the vessel after it crashed.

While the number of cars in the water remains unknown, a tractor-trailer was one of the vehicles believed to be on the bridge when it came down, according to CBS News.

The bridge has been closed to traffic after the collapse, according to transport chiefs.

"I can confirm at 1:35am, Baltimore City police were notified of a partial bridge collapse, with workers possibly in the water, at the Francis Scott Key Bridge," a cop said.

The Baltimore Fire Department Chief James Wallace was reported as saying that at least two people have been rescued so far with one having no injury while the other in critical condition.

Authorities are currently searching for 20 people but, Wallace said that officials are searching for upwards of seven people.

The bridge, which was built in 1977, is part of Maryland’s Interstate 695 and is one of the longest truss bridges in the world, with over 11 million cars travelling over it annually.